The effect of the UV radiation is studied to investigate the optical properties of CR-39 polymer. The measurements of FTIR spectroscopy show maintenance of the main vibratory band resulting from the irradiation times. The optical absorption spectrum of UV / VS indicates a main alteration in the optical energy gap with irradiation times. From the results, it was found that increasing the irradiation time of CR-39 by UV-lamp leads to an increase in the sensitivity of the detector and improvement of its properties and thus achieve safe use of these detctors. FTIR spectra shows the conservation of the distinctive spectral peaks related to the monomer of polymer before and after exposure to different intensities of UV-lamp. From this results, the CR-39 detector ultraviolet irradiated were conformed to be very sensitive to UV radiation.